[antlr-interest] How to distinguish between integer an binary number?

[Mario Prada]

Finally, I implemented the proposed new rule, and it works fine :-)
(redefining the language wan´t an option)

Thanks all.


On Sun, Dec 14, 2008 at 12:15 AM, Gavin Lambert <antlr at mirality.co.nz>wrote:

> At 09:31 14/12/2008, Johannes Luber wrote:
> >Mario Prada schrieb:
> >> I need to distinguish between integer an binary number in
> >> my grammar.<P>
> [...]
> >You actually can't do that in the lexer. ANTLR does lexing all
> >in-front, before even the parser sees the first token. Thus
> >all numbers fitting the binary pattern are BINARIOs, even if
> >they are supposed to be normal numbers. The solution is make
> >one lexer rule for all kinds of numbers and to check only in
> >the parser, if a number contains only zeros and ones.
>
> Another possibility is to replace all usages of "INT" in the parser with
> "integer", then define a new rule like so:
>
> integer : INT | BINARIO;
>
> This way the lexer will still generate distinct INT and BINARIO tokens, but
> if the parser context is expecting an integer, it will accept both.  (If
> you're building an AST, you will probably also want to add a rewrite to
> convert the BINARIO token to an INT token for the AST.)
>
> As Sohail said, though, if you have the luxury of (re)defining the language
> then you should consider adding some lexically-obvious prefix or suffix to
> distinguish binary constants from decimal constants.  That should help to
> remove some of the confusion both on ANTLR's part and potentially that of
> anyone reading the input file.
>
>


-- 
Mario Prada Arroyo
----------------------------------------------------------------------------------------------------------
Todo hombre tiene una mujer que lo espera, el caso es llegar a tiempo
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